As semiconductor chips and electronic parts are required to be configured in small and thin size, and as high-definition liquid crystal displays have been developed, circuits and electrodes therefor are required to have high density and high definition. It is difficult to connect such microelectrodes by soldering. Thus, recently the microelectrodes have been often connected using an adhesive.
There are some methods for connecting electrodes using the adhesive. In one of such methods, an anisotropic conductive adhesive or film containing conductive particles such as particles of carbon, nickel or metal-coated plastic in an insulative adhesive is pressed with heat to produce an ACF (=anisotropic conductive film) which gives electrical connection in a thickness direction of the adhesive (Patent Document 1, the method may be referred to hereinbelow as ACF). In another method, in the absence of the electroconductive particles, concavo-convex shapes of the electrode surface were directly contacted upon applying pressure on NCF (non-conductive film), to thereby establishing electrical connection (Patent Document 2, the method may be referred to hereinbelow as NCF).
In recent years, for electrode semiconductor substrates with ACF connection, a liquid crystal driver IC has been mounted by a COG (chip on glass) system or a COF (chip on flexible print circuit board) system. On a surface of such driver IC, a heat resistant resin composition such as a polyimide film or a polybenzoxazole film is widely used. The heat resistant resin composition and the adhesive film such as ACF and NCF have to be adhered with an excellent adhesiveness. Particularly, such chips are required to keep highly reliable adhesiveness after being mounted even in a thermal shock cycle resistance test and a high temperature high humidity test.
As a procedure to enhance the adhesiveness between the heat resistant resin polyimide film and ACF, Patent Document 3 discloses technology for enhancing the adhesiveness by treating the polyimide film with plasma. Patent Document 4 also discloses the technology for enhancing the adhesiveness by treating the polyimide film with plasma at low temperature.
Patent Document 1: JP Sho-55-104007-A    Patent Document 2: JP Sho-60-262430-A    Patent Document 3: JP 2003-73862-A    Patent Document 4: JP 2003-163451-A